overlap

Overlap is a small scheduling poll. You pick a few days and a window of hours, share one link, and everyone drags across the times they can make. The page then answers in one sentence, like "Tue 11:30 AM–1:00 PM works for everyone", written in each person's own timezone.

There are no accounts. Creating a poll gives you two links: a public one to share, and a secret one that's the only way to edit or delete the poll.

What it does

• Timezones done properly. Everyone sees the grid in their own timezone, with their own 12- or 24-hour clock and their own first day of the week.
• Fair to every timezone. When times are tied, the one that falls between 08:00 and 21:00 for the most people wins, and the answer says who it's early or late for.
• "If needed" answers. You can mark a time you can make, or one you'd rather not but could.
• Fill in from your calendar. Pick an .ics export and every free time gets marked. The file is read in the browser and never uploaded.
• Live. New answers show up on every open page without a reload.
• And the rest: weekly polls, meeting length, people who must be there, deadlines, and a CSV export.

How it's built

The whole app runs on one Cloudflare Worker: Next.js through OpenNext, D1 for the data, and a Durable Object per poll for live updates.

• The secret link is never stored. The database keeps a hash of it, so a copy of the data can't be used to edit anything.
• Live updates carry no data. Each open page only hears "changed", then re-renders on the server for its own viewer.
• Working around limits. D1 accepts at most 100 values per query, so each person's answers are saved as a single JSON value.
• Weekly polls are one real week. They're stored as a reference week, so the rest of the app didn't need to know they were weekly.